1. Field of the Invention
The present invention relates to a channel plate used for an image intensifier, a photoelectron amplifier and so on and a manufacturing method thereof.
2. Related Background Art
An electron multiplier using a secondary electron emission phenomenon, such as a photomultiplier, is widely in the actual use. The electron multiplier has a mechanism having a channel comprised of an interior wall of a glass pipe or a ceramic pipe, wherein an electron accelerated by an electric field is collided against the surface of the wall of the channel to generate a plurality of secondary electrons. Such electron multipliers are made in micro-size and integrated in a high density so as to form a channel plate of a planar structure (also called a multi-channel plate, micro-channel plate and so on), which is used for an image device such as an image intensifier. In recent years, as requirements for the image device, not only more higher level of performance such as higher density, higher sensitivity, higher-speed operation and wider dynamic range, but also larger a size design more than the micro-size and a simple production method in order to provide a device with larger area and higher resolution. For that purpose, a large channel plate wherein electron multipliers are integrated in a density higher than the micro-size is required.
For higher resolution of channel plate, it is necessary to integrate individual electron multiplier in a high density. For that purpose, it is desired that channel wall thickness to each channel opening is small. Moreover, a plate having a stable channel wall hardly destructible over large area is required for a large-size channel plate that is larger than the micro-size.
The conventional electron multiplier uses glass such as lead glass and ceramics because of the necessity to form a tubular internal wall surface. The conventional multi-channel plate is formed by extending bundled glass pipes in a heated and softened state to form a plate having many pipes, or as shown in Japanese Patent Application Laid-Open No. 2000-113851, or, it is formed by coating a wire surface with diamond film, adhering the coated wire with an insulating substrate such as a plurality of adhesives, cutting the insulating substrate into plate-like elements, removing the wire by etching to form electrodes on both sides of the plate-like element respectively, or as shown in Japanese Patent Application Laid-Open No. 4-87247, it is formed by forming a pipe on a high lead glass substrate by etching and then heat-treating it in reducing gas atmosphere such as hydrogen.
FIG. 5 is a perspective view illustration showing configuration of the conventional channel plate. On a glass insulating substrate 21, a plurality of channels 22 are formed by etching, and a cathode electrode 24 and an anode electrode not shown therein are formed.
As for the conventional channel plate formed by using glass, it is necessary to decrease a diameter of the channel opening such that the diameter is smaller than the channel wall thickness in order to enhance strength of the glass to be the substrate. Accordingly, it is possible to make it larger but there is a limit to making it higher-resolution in the case of using a glass substrate as the substrate.
In addition, while the method of forming pores by cutting glass pipes or wires after bundling them in an adhesive layer and etching them is suitable for rendering a small plate higher-resolution, it is necessary to enhance adhesive strength against the etching for the purpose to allow the larger area design. Accordingly, the area occupied by the adhesive layer in the pore opening must be large enough. Moreover, in these methods, a semiconductor layer may be formed by heating the channel internal wall glass surface at high temperature in reducing atmosphere such as hydrogen. In such cases, a problem of heat strains due to high temperature heat treatment arises. Furthermore, as the wire to be a mold of the electron multiplier surface is removed by strong acid etching after forming a coating of diamond and so on, it was necessary to form the electron multiplier surface, which is the coating, as a robust coating that is maintained even without the wire.
The present invention was implemented in order to solve the problem set forth above, and its object is to provide a multi-channel plate that has high resolution and is advantageous for larger area, high resolution design and a manufacturing method thereof.
Another object of the present invention is to provide a channel plate having a structure of an electron multiplier surface capable of increasing a secondary electron multiplication factor and the manufacturing method thereof.
To be more specific, the channel plate according to the present invention is one having a porous element, and is characterized by the porous element including an aluminum compound.
In addition, the channel plate involved in a second invention of the present invention comprises: a substrate; a first electrode placed on the top face of the substrate; and a second electrode placed on the bottom face of the substrate, wherein the substrate is the porous element having a plurality of pores extending therethrough, and the porous element is formed with a compound including aluminum, and the porous element has an electron multiplier on a wall surface of the pore.
It is desirable that the above described electron multiplier emits secondary electrons due to collision of the electrons with the above described electron multiplier.
It is desirable that the above described electron multiplier has oxide grains of which secondary electron emission coefficient is larger than 1.
It is desirable that the above described porous element has aluminum oxide as its main ingredient.
It is desirable that the above described electron multiplier is formed by coating the wall surface of the pore of the above described porous element.
In addition, a third invention of the present invention is a channel plate manufacturing method comprising the steps of: anodizing aluminum or the substrate of which main ingredient is aluminum to form the porous element having a plurality of pores extending through the substrate; forming the electron multipliers on the wall surface of the pores; and forming the electrodes on the top and bottom faces of the porous element respectively.
It is desirable that the above described step of forming the electron multipliers is a step of coating the wall surfaces of the pores of the above described porous element with a coating layer including a material of which secondary electron emission coefficient is larger than that of the material forming the above described porous element.
It is desirable that the above described coating layer comprises a material of which secondary electron emission coefficient is larger than 1.
It is desirable that the above described aluminum or the substrate of which main ingredient is aluminum is an aluminum film disposed on the electrode to be anodized.
It is desirable that the above described coating layer includes oxide grains.
According to the present invention, it is possible to provide the channel plate wherein a channel having the electron multiplier surface of which electron multiplication factor is improved is formed over large area. It is possible, by using this channel plate, to acquire a large image intensifier of high resolution and large area, which can meet the demand for larger area design and higher performance in recent years.